HTTP cache / validator / 304
Separate ETag, Last-Modified, Cache-Control and 304
Use synthetic headers to separate freshness from revalidation. No real URL is contacted; only a local handoff note is saved.
Four decision axes
ETag is a representation validator, Last-Modified is a date validator, and Cache-Control describes freshness and revalidation. A 304 is returned when a conditional request validator matches.
ETag + If-None-Match → 304 / Last-Modified + If-Modified-Since → 304 / Cache-Control: no-cache → revalidate before use / Cache-Control: max-age → fresh until stale| Axis | Review |
|---|---|
| ETag | Compare the representation identifier with If-None-Match. |
| Last-Modified | Compare the date with If-Modified-Since. |
| no-cache | It requires validation before use; it is not no-store. |
| max-age | The response is fresh until the age expires. |
Review boundary
- Record the response validator.
- Compare it with the conditional request value.
- Treat a match as 304 and a mismatch as a new representation.
- Separate storage, freshness and revalidation in the handoff.
This page does not contact a real server. Review live delivery settings with service logs and an approved procedure.
Six synthetic cases
| case | result |
|---|---|
etag-match-304 | 304 Not Modified |
last-modified-304 | 304 Not Modified |
cache-control-no-cache | Revalidate |
cache-control-max-age | Fresh until stale |
validator-mismatch | 200 OK / new representation |
unsupported-network-request | Reject |